[patch] libertas: fix write past end of array in mesh_id_get()

[patch] libertas: fix write past end of array in mesh_id_get()

[Dan Carpenter]

defs.meshie.val.mesh_id is 32 chars long.  It's not supposed to be NUL
terminated.  This code puts a terminator on the end to make it easier to
print to sysfs.  The problem is that if the mesh_id fills the entire
buffer the original code puts the terminator one spot past the end.

The way the original code was written, there was a check to make sure
that maxlen was less than PAGE_SIZE.  Since we know that maxlen is at
most 34 chars, I just removed the check.

Signed-off-by: Dan Carpenter <error27@gmail.com>

diff --git a/drivers/net/wireless/libertas/mesh.c b/drivers/net/wireless/libertas/mesh.c
index acf3bf6..9d097b9 100644
--- a/drivers/net/wireless/libertas/mesh.c
+++ b/drivers/net/wireless/libertas/mesh.c
@@ -918,7 +918,6 @@ static ssize_t mesh_id_get(struct device *dev, struct device_attribute *attr,
 			   char *buf)
 {
 	struct mrvl_mesh_defaults defs;
-	int maxlen;
 	int ret;
 
 	ret = mesh_get_default_parameters(dev, &defs);
@@ -931,13 +930,11 @@ static ssize_t mesh_id_get(struct device *dev, struct device_attribute *attr,
 		defs.meshie.val.mesh_id_len = IEEE80211_MAX_SSID_LEN;
 	}
 
-	/* SSID not null terminated: reserve room for \0 + \n */
-	maxlen = defs.meshie.val.mesh_id_len + 2;
-	maxlen = (PAGE_SIZE > maxlen) ? maxlen : PAGE_SIZE;
+	memcpy(buf, defs.meshie.val.mesh_id, defs.meshie.val.mesh_id_len);
+	buf[defs.meshie.val.mesh_id_len] = '\n';
+	buf[defs.meshie.val.mesh_id_len + 1] = '\0';
 
-	defs.meshie.val.mesh_id[defs.meshie.val.mesh_id_len] = '\0';
-
-	return snprintf(buf, maxlen, "%s\n", defs.meshie.val.mesh_id);
+	return defs.meshie.val.mesh_id_len + 1;
 }
 
 /**

Re: [patch] libertas: fix write past end of array in mesh_id_get()

[Dan Williams]

On Thu, 2011-03-10 at 18:23 +0300, Dan Carpenter wrote:
> defs.meshie.val.mesh_id is 32 chars long.  It's not supposed to be NUL
> terminated.  This code puts a terminator on the end to make it easier to
> print to sysfs.  The problem is that if the mesh_id fills the entire
> buffer the original code puts the terminator one spot past the end.
> 
> The way the original code was written, there was a check to make sure
> that maxlen was less than PAGE_SIZE.  Since we know that maxlen is at
> most 34 chars, I just removed the check.
> 
> Signed-off-by: Dan Carpenter <error27@gmail.com>

Acked-by: Dan Williams <dcbw@redhat.com>

> diff --git a/drivers/net/wireless/libertas/mesh.c b/drivers/net/wireless/libertas/mesh.c
> index acf3bf6..9d097b9 100644
> --- a/drivers/net/wireless/libertas/mesh.c
> +++ b/drivers/net/wireless/libertas/mesh.c
> @@ -918,7 +918,6 @@ static ssize_t mesh_id_get(struct device *dev, struct device_attribute *attr,
>  			   char *buf)
>  {
>  	struct mrvl_mesh_defaults defs;
> -	int maxlen;
>  	int ret;
>  
>  	ret = mesh_get_default_parameters(dev, &defs);
> @@ -931,13 +930,11 @@ static ssize_t mesh_id_get(struct device *dev, struct device_attribute *attr,
>  		defs.meshie.val.mesh_id_len = IEEE80211_MAX_SSID_LEN;
>  	}
>  
> -	/* SSID not null terminated: reserve room for \0 + \n */
> -	maxlen = defs.meshie.val.mesh_id_len + 2;
> -	maxlen = (PAGE_SIZE > maxlen) ? maxlen : PAGE_SIZE;
> +	memcpy(buf, defs.meshie.val.mesh_id, defs.meshie.val.mesh_id_len);
> +	buf[defs.meshie.val.mesh_id_len] = '\n';
> +	buf[defs.meshie.val.mesh_id_len + 1] = '\0';
>  
> -	defs.meshie.val.mesh_id[defs.meshie.val.mesh_id_len] = '\0';
> -
> -	return snprintf(buf, maxlen, "%s\n", defs.meshie.val.mesh_id);
> +	return defs.meshie.val.mesh_id_len + 1;
>  }
>  
>  /**
> --
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